Photographic objective.



. these suppositions No. ,ascesa UNITED STATES PATENT "OFFICE -,j Patented my 10, 1904 KARL MARTIN, 0E RATHENOW; GERMANY,

OIYIISCHE INDUSTRIE, ANS'IALT, VORMALS EMIL BUSCH, A.G., 0F RA'IHENOW, GERMANLA FIRM.. A

PHoToenAPi-Iioosuscjjivg.

SPECIFICATIN forming part o Letters Patent No. 759,537, dated MCB-'y 10, 1904. l

AssIGNoR To RATHENQWER naman am oww s, m1. snm n. 71,445. fue man.)

To all whom it may concern:

Be it known that I, KARL MARTIN, a subject of the King of Prussia, German Emperor, and a resident of Rathenow, in the Kingdom of Prussia, German Empire, have invented certain' new and'useful Improvements in Photographic Objectives, of which the following is an exact specification.

My invention relates to improvements in photographic objectives, and has especially for its purpose to provide an objectivewithtwo lenses, which objective is spherieally,

chromatically` and astigmatically corrected. 1t has been tried in the last years with g success to Ilse the Gauss (telescope) objective for photographie purposes by correcting the astigmatic faults of the same.

It could be supposed that in ease of means being found for attaining an astigmatic correction for photographic objectives with two lenses, so-called Gauss objectives, these objectives would possess all the advantages connected with this (iauss type. Indeed, it hasbeen proved by the construction of the so-called "Zeiss-Planar objective that the Aanastgmatic Gauss objective is one of the best Ahitherto constructed. Y of the new construction consisted In the same The only disadvantage not being perfectly chl'omatically correctable. This disadvantage has been tried to do away with by constructing' ,the two lenses forming the anastigmatic objective in the well-known manner from two glasses with nearly the same refraction, but diterent'dispension. ln this manner the chromatical correction was attained in an indirect way. 1t has been tried also to attain a chromatical correction of sai type by means of single lenses, which could, however, be a ttained only when desisting from the advantage of a great opening. 'lll new it was believed that the chromatical correction could only be attained by using a very heavy flint-glass, which on account of want of firmness is unlit for photographic purposes, or by using a crown-glass (for the positive lens) with n. higher refraction than that of the Hint-glass of the negative lens. Both havel proved to incorrect. Now it has been found by starting, for instance, in the calculation from a intglass with the index 1.60 and a crown-glass with `the index 1.50 that after the objective bein spherically and astigmatieally corrected, al the chromatieal correction can be attained bymeans of regularI glasses.

In the accompanying drawings, in Figure 1 an example of an objective constructed according tomy new invention is shown. Fig. 2 shows the use of the same in a double-lens system.

The opening of the system, Awhich is exactly. spherically corrected, amounts to one. eleventh. ln spite of this great opening the spherical '/.one fault amounts only to 0.25 millimeter in case of. a focal distance of one to two hundred and lt is very easy to lind out similar sets of glasses in which a correction is possible.

In the two lens objectivesdescribed, for instance, in the United States Letters Patent to Clark,No. 399,499, an astigmatie planing of the lield-that is to say, could never be obtained on account of the curves of the surfaces of the lenses not standing in the right proportions. The removing 1)..: 5.73 esce 1.4967 1 .50527 hundred millimeters, so that by small changes j The equivalent D.: 6.15 0.318 ti feas-8T; Y

an astgmatic correctionl of the anastigmatism andthe lield curve isl obtained according to my invention by giving Two systems constructed as described above to the negative meniscus lens of the system a can advantageously be used for constructing suliiciently hollow form f or compensati-ng the holo and hemi symmetrical double-objectives nnnstigrnatic faults for the positive mcuiseus as shown in Fig. 2, inA which case smalldier- 4o 5 lens. This new construction forms the object ences between the two sets may be very adof the present invention and renders my new vantageous for correcting small faults'of the objective different from the older Gauss syswhole system. By means of the double obtems, which were not astgmatically corrected, jectives so constructed a density of light up to as in the'same the concave lens had no sutiiabout F 3.9 can be-attained.-

M IQ cient capacity of planing the tield. The best Having thus fully described the nature of form of lenses is obtained-zl e., the astigmamy said invention, what'I desire to secure by tism and the field curve are best removcd- Letters Patent of the United States iswhen constructing the lenses so that the sum 1. A photographic objective, consisting of i 'of the diierences in the curves ofboth lenses\ a negative meniscus of higher refraction and 59 15 is perfectly or about equal to zero. This will a positive lens of lower refraction, which are be more clear when considering the following arranged so as to leave a space'between them calculation: which has the form of a negative lens, the' The curve of the surface of the lens is sum of the `di`erences in the curve of both called R. The reciprocal value of thelatter for lenses being about equal to zero, substantially 55 2o the focal distance equals one. Consequently as described. and for the purpose set forthw ,I

focal distance or p For 2, A'photographic objective, consisting of v radius R' twol sets Aeach consisting of .'a meniscus o'f the example given above the calculation the`n higher refraction and apositive lens of lower 1 gives the following result: refraction, which are arranged so 'asta leave 6o -25 p 6.02 2 86 a space between them, which hasthe form of 3.16 A o 8 fa negative lens, the sum, of the differences' in curve equals pg: 0.35 M 3 ,66 the curve of both lenses being about equal to pa: 4.01 I zero, substantiallyas described and for the The fact that the value A is in my system.` purpose set forth. 65

- 3o nearly equal to' zero (=0.8) forms the im- IntestmonywhereofIhavesgnedmyname portant feature .o f my invention, as by this'. tothis specification in the'presence of twosubfact the anastig'matic planing' othe tieldis 'scribingwitnessea 'f obtained. In an objectives hitherto com. y' KARL MARTIN, Vstructed the value A will be three or four. Wtnesses'affA v 35 times greater, which` isthe' reason for the 4HENRY Heerlen,-

astigmatic faults of these systems.' y l. -i WoLDmpui 

